Non-rechargeable batteries and rechargeable batteries produce current the same way, which is through an electrochemical reaction involving an anode, cathode and electrolyte. The advantage that the rechargeable battery has is that the reaction is reversible. When electrical energy from an outside source is applied to a rechargeable cell, the negative-to-positive electron flow that occurs during discharge is reversed, and the cell's charge is restored.
However, after a number of recharge cycles, rechargeable batteries can lose discharge capacity. For example, if these batteries were not fully discharged every time they were used, they would quickly lose capacity. This means the batteries were able to discharge less energy than when in their new condition. This is known as the memory effect.
With some battery chemistry types, discharge capacity can be reconditioned by “auto-cycling,” which is the process of fully discharging and recharging the battery one or several times. Equipment that is designed to recondition a battery in this way simply discharges the battery through a current resistive device and “wastes” the energy by converting the energy to heat. In most situations, this is acceptable because the cost of wasted energy is very small and the waste heat is easily transferred to the environment.
However, in some circumstances, the energy cost may be more meaningful, or the waste heat may be more difficult to dissipate. Such is the case for the batteries used in spacecraft. For example, the International Space Station can provide only limited cooling capacity to a battery charger module, which also performs the auto-cycling for spacesuit batteries. As such, it would be useful to reduce the waste heat in this type of situation.